The maintubes are milled from a solid piece of 6061-T6 aircraft aluminum. The 30mm diameter provides enough room for extended travel of the Windage and elevation adjustments.

The oversize Windage and elevation knobs on the Mark 4 M1-10x40mm are easy to grip. Plus, you get audible and tactile feedback from the 1/4-MOA clicks. Once sighted-in, the knobs can be zeroed. Also, the elevation knob has a horizontal scale that allows you to count adjustment revolutions.

Mark 4 scopes also employ a turret-mounted focus knob that lets you adjust out parallax for specific ranges, from 50 yards to infinity, in a shooting position without taking your eye off of the target.